At present, employed in looms currently in use, shuttleless (with microshuttles) and rapier looms included, is a conventional method of cloth formation based on a cyclic principle of performing different operations, namely, shedding, weft propulsion, warp tension (length) compensation at shedding, adjustment of different amounts of tension applied to tight and slack shed sides and beating-up of the weft thread to the fell of the cloth as well as the warp let-off and the cloth take-up. Compensation of the tension applied to the warp threads at shedding is attained at the loom with a rocking back-rest, the difference in amounts of tension applied to the tight and slack shed sides being created by a lease rod. Naturally, the type of the produced cloth governs the weaving particulars: the lifting height of the back-rest above the breast beam, the amount of shift of the back-rest at the compensation of tension during shedding, the relation of amounts of tension applied to shed sides, the amount of crossed shed and beat-up angle.
In looms equipped with a shedding mechanism, weft thread propulsion and beat-up mechanisms, warp let-off motion and cloth take-up means, there is a known apparatus ensuring different amounts of tension applied to the shed sides (cf. German Federal Republic Pat. No. 1,255,599; Cl. 86C. 86C 18/11). The apparatus providing for different amounts of tension applied to the shed sides includes guiding rods installed so as to be able to execute alternating oscillatory up and down motion in the shed and creating definite tension exerted on the warp threads during weaving.
In the process of weaving, the warp threads on these looms undergo a great tension persistently growing till the beat-up moment, and the amount of which considerably exceeds the necessary tension and which is set and maintained during the entire cycle of cloth formation, i.e. while the main shaft of the loom turns through 360.degree..
The keeping of the warp threads under an increased tension mainly stems from a necessity to create suitable conditions for beating up the weft thread to the fell of the cloth within the loom working cycle, i.e. within a 360.degree. angle of turn of the main shaft and this, to a large measure, adds to yarn fatigue due to multiple loads which, in the final analysis, causes broken ends, defects in cloths and equipment time-outs. Especially, this manifests itself in attempts to produce with the shuttleless looms, outfitted with microshuttles or rapiers, the cloths from bast yarns which are most rigid and least extensible and possess great lengthwise irregularity, or in attempts to produce from any yarns the cloths of increased weft density.